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References: <20181220111008.24954-1-alex.bennee@linaro.org>
	<20181221193037.GB11197@flamenco>
From: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <72dff278-24d4-61db-3b49-a50a5aec6448@linaro.org>
Date: Fri, 21 Dec 2018 14:01:02 -0800
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Subject: Re: [Qemu-devel] [RFC PATCH] fpu: add compile time check for old
 glibc/libm and fma
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To: "Emilio G. Cota" <cota@braap.org>, =?UTF-8?Q?Alex_Benn=c3=a9e?= <alex.bennee@linaro.org>
Cc: laurent.desnogues@gmail.com, Peter Maydell <peter.maydell@linaro.org>, qemu-devel@nongnu.org, Aurelien Jarno <aurelien@aurel32.net>

On 12/21/18 11:30 AM, Emilio G. Cota wrote:
> +    ua.s = 0x0020000000000001;
> +    ub.s = 0x3ca0000000000000;
> +    uc.s = 0x0020000000000000;
> +    ur.h = fma(ua.h, ub.h, uc.h);
> +    if (ur.s != 0x0020000000000001) {

Forgot your ull's, but otherwise ok.

In email to Alex, I did wonder if we should check for fma hardware (at least on
x86).  Without a hardware insn, the libm routine is probably no faster than
softmmu.


r~